1. Field of the Invention
This invention relates to a liquid separating apparatus for extracting liquids different in kind from a container such as a blood bag which possesses flexibility and has sealed therein the different liquids separated into plural layers.
2. Description of the Prior Art
Recently, instead of using whole blood for transfusion, the practice of transfusing only necessary blood components to patients in need of such components (componential transfusion) or the practice of collecting only plasma from blood for the purpose of preparing plasma medicines has been in vogue. For the purpose of securing the blood to be used in the componential transfusion or the manufacture of plasma medicines, the flexible blood bag which is popularly called "multiple-bag" has been heretofore used. This blood bag (container) is composed of a blood collecting bag (primary bag) for containing the blood collected from a donor and one or more separation bags (satellite bag) communicating with the primary bag through the medium of a liquid extracting tube (hereinafter referred to simply as "tube"). The blood components separated by the use of a centrifuge and held in the primary bag are extracted independently of each other and transferred into the satellite bags.
When the blood collecting bag is treated with a centrifuge, the blood in the bag is separated into such layers of different components as a plasma layer, a red blood cell layer and an intermediate layer (a soft membranous layer containing platelets, white blood cells etc., so-called buffy coat layer). For these separated blood components to be utilized per se afterward, it is necessary that these components should be collected independently of each other from the blood collecting bag and stored respectively in the separation bags lest they should commingle.
The fractional collection of such blood components has been heretofore accomplished by subjecting the blood bag to the action of a liquid separating device and then compressing the blood bag with pressure exerted on the opposite surfaces thereof thereby allowing the separated components to be transferred into the relevant separation bags through the relevant component extracting tubes which communicate with the blood bag.
The componential extraction of blood is not easily attained by the use of the blood bag of the kind which, as disclosed in JP-A-3-47,266, is provided in the upper part thereof with blood collecting tubes or component extracting tubes. Particularly when the intermediate layer is to be extracted into the satellite bag, it is difficult to choose apt timing for extracting the intermediate layer from the inner wall of the primary bag. Thus the controllability of the blood bag is at a disadvantage and the intermediate layer is apt to remain inthe primary bag.
In the case of the blood bag which, as disclosed in JP-B-63-20,144, is provided with tubes disposed in the upper and lower parts of the primary bag, the componential extraction is attained rather easily. Since the ports to be used for the extraction are disposed at the upper and lower edges of the bag proper, however, the tubes are not handled conveniently during the attachment of the bag to the centrifuge or the blood component separating device.
In the case of the blood bag which, as disclosed in EP-A-0484751A1, is provided with a separation path, ie. a conduit formed in the interior part of the primary bag by bonding or fusion of opposed ribbonlike portions of the inner wall surfaces of the bag, for guiding the liquid of the lower layer to the upper part of the bag proper, the accuracy of collection of red blood cell is decreased in proportion as the width of the path is increased because parts of the plasma component and the intermediate layer component are present besides part of the red blood cell of the lower layer in the path after the step of centrifugal separation. If the width of the path is decreased for the purpose of heightening the accuracy of collection, the uncomfortable possibility arises that the time to be required for the extraction increases and the speed of flow of the blood through the path immensely increases. If the path is endowed with a more or less sizable width, the accuracy of collection of the red blood cell component is lowered. When the blood components fractionally collected by the blood bag using this path of the sizable width are put to use, there ensues the necessity for these components being deprived of impurities by the use of such an instrument as a white blood cell removing filter or a varying adsorbent. The measure of thermally fusing the opposed walls of the primary bag requires formation of a sealed part extending to the bottom part of the bag and results in an increase of steps forming the process of manufacture. During the attachment of the primary bag to the blood separation device, the convenience with which the primary bag is handled is impaired because the portions of the opposed walls of the bag which are available for the attachment are fixed.
By the manner in which the primary bag is compressed after undergoing centrifugal separation, the liquid separating devices are classified into those of the lower biased pressure type disclosed in JP-B-55-17,585 and those of the parallel compression type disclosed in JP-A-55-155,652. The devices of the former type are intended to operate by suspending a primary bag from a hook provided on a separation stand and compressing the suspended primary bag with pressure exerted on the opposite walls of the bag by means of a pressing plate so supported as to render the lower end thereof rotatable and the devices of the latter type by placing a pressing plate parallelly to a separation stand and interposing a primary bag between the separation stand and the pressing plate and pressing the pressing plate across the interposed bag against the separation stand with pressure exerted on the opposite walls of the bag.
Some of these liquid separating devices are adapted to effect the application of pressure automatically or manually. The liquid separating devices capable of automatic application of pressure which have been finding extensive utility, without discrimination between the two types mentioned above, are intended to operate by continuing detection of the position of an intermediate layer by means of an interface sensor and meanwhile compressing the bag by means of a pressing plate.
These conventional liquid separating devices are invariably intended to expel the blood from the bag by the application of pressure to the bag and are not devised to ensure or aid in the discharge of the blood as by altering the shape or construction of the bag itself. Thus, they find utility only in limited applications.